Remove beta badge on suggested reviewers settings

What does this MR do and why?

This MR removes the beta badge on suggested reviewers' settings. This feature is ready for GA and we are in the process of removing the feature flag altogether.

This setting is behind a feature flag suggested_reviewers_control so no change log is required.

Relates to #368356 (closed).

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Ensure a SaaS (Gitlab.com) environment
   1. One way of doing this is to add a env.runit file to the root GDK folder with the following snippet

      export GITLAB_SIMULATE_SAAS=1

2. Set ultimate license on a group http://gdk.test:3000/admin/groups
3. Create a project in the ultimate group or use an existing one, e.g. http://gdk.test:3000/gitlab-org/gitlab-test
4. Set the feature flag on rails console bundle exec rails c

   project = Project.find(2)
   Feature.enable(:suggested_reviewers_control, project)

5. Login as a user with Maintainer role
6. Navigate to Project settings > Merge Requests page, e.g.http://gdk.test:3000/gitlab-org/gitlab-shell/-/settings/merge_requests
7. Observe the Suggested Reviewers section

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.